The ionic basis for the electrical signaling properties of vertebrate retinal neurons will be studied. Isolated, single neurons maintained in tissue culture from carp, perch and skate retina will be used. Single horizontal cells will be studied to determine the properties of the ionic channels present in the membrane. These cells will also be used to determine the ionic basis for their response to putative photoreceptor neurotransmitters. Single, cultured bipolar cells will be studied to determine the types of ionic channels present as well as to determine the ionic basis for their activation by photoreceptor transmitters. Isolated ganglion cells will be studied to determine the characteristics of the ionic channels present in the membrane. They will also be studied to determine the effects putative bipolar cell and amacrine cell transmitters have on membrane currents. Patch clamp techniques will be employed so that the properties of macroscopic currents as well as single channel currents can be described. The use of isolated retinal neurons is a powerful tool which allows us to study the physiology of retinal cells outside of the retinal network. Thus, information can be gathered that was previously inaccessible. Yet the approach selects out particular cells. Experiments will be done to try to improve the technique such that qualitatively better cells result as well as improving the cell yield. It is anticipated that the proposed study will provide information on the properties of ionic channels in retinal cell membranes as well as how these channels are modulated by neurotransmitter agents. This will lead to a better understanding of how the individual cells process information and as a result increase our knowledge of how the retina as a whole processes the visual signal.